Go Down

Topic: Vehicle Detection Sensor- Any Recommendation?? (Read 3104 times) previous topic - next topic

magsens

Hi all,

I am working on a school project. The idea is to detect a car as it parks or as it leaves a parking spot. So, a sensor that can transmit a "1" when a car is over it or a "0" otherwise. I was looking to honeywell HMC1001 magnetic sensor. however I am not sure about it.
Can you suggest any sensor that can be easily connected to arduino and which does the job?

Any help is appreciated!

GoForSmoke

Just going by commercial units you may need area below to sense distance above. Or maybe that's just because some cars don't use so much magnetic metals.

You could use a magnet to make a field and see if you can detect change in the field when a car is above or not with a Hall sensor. Making the magnet an electromagnet will let you make the field move and induce a counter-field(s) in iron part(s) that may detect better. I dunno but if you actually try it should count towards grade.

Me, I'd be making pressure strips.


Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

magsens

Thank You for the suggestions.
I was reading somewhere that the Hall sensors is not a good idea. A suggestions I saw was HoneyWell HMC1001. I wasnt sure, so I thought maybe I get some good feedback here.

GoForSmoke

Hall sensors are good enough for instrument work if you get the precise ones.

The magnetic compass ones are amplified more. Park a car over one of those and watch "north" change?



Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

magsens

I was reading that there is some magnetic change and this type of sensor is too sensitive. But I am not sure if it will work that's why I opened this thread for some better suggestions.

GoForSmoke

It is simple. Have you ever used an ordinary hand held magnetic compass?

If you hold it down by your waist and you have a heavy iron/steel belt buckle the the compass always points to or away from you, more due to proximity than mass of the metal to compass.

If you bury one center of parking spot how far away could a car or truck park and the sensor point to that? Next slot over? 2 slots over? Reality check: take a hand compass out in a parking lot and see what effect cars have on it at different distances. It tails off real quick.

That's using a digital compass which is passive. You can go active and use a Hall to monitor the field, even pick up induced fields. Have a coil circuit put out a strong burst and look for a return every 10 to 30 seconds.

You might check out capacitive sensing. People can be sensed standing a meter from a wall that was painted with conductive paint using capacitive sensing. You'd also do well to find a metal detector circuit.


Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

Neight

why not use an IR or ultrasound distance sensor?

you wouldn't have to fiddle with magnetic anything, just tell the arduino if the sensor detects an object closer than 12" over the sensor, there is a car there.
put the sensor right in the middle of the parking space, so it wont miss the vehicle.
you could also program it to dismiss counting objects that are over the sensor for less than 1 minute.  That way, if someone walks over it or something else like that, it wont record that as a parked car. 

this seems like a much more simple option, and more reliable than a magnetic sensor.
if the parking space is in a lit parking garage, you could also use a light dependent resistor.  when a car is over the sensor, it would be darker.  even at night in a lit garage.  you would just have to tinker with it to find a darkness level at witch to trigger the action you are looking for.

Just a few ideas I had, figured I would share :)
N8
absence of proof is not proof of absence

Papa G

Another approach would be to put a large coil of wire where the car is to park. Use enough turns to get a measurable amount of inductance and use that inductance as the basis for an oscillator. When there is no metal interfering with the inductance of the coil, the oscillator will be at its design frequency. When ferrous metal interferes as when a car moves over the coil, the frequency will change.

GoForSmoke

It's probably better to use a buried sensor that's immune to rain, dirt, oil drips and spills.

I remember ultrasound on traffic lights in the 70's. It got replaced with buried sensors.

You could try force/pressure sensors, make car-size stomp boxes....
Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

magsens

Thank You for the ideas.
I like Neight idea. I think might be easier to manage the distance.
Do you know any type of sensors (ultrasonic) that is not a hassle to connect to arduino?

GoForSmoke

Yeah. They're good to 4.5 meters in the best conditions, not happy with rain and put down in the middle of parking spaces not likely to last a whole season especially once they're noticed by the FTW crowd. But you can put them up on poles and close the lot when it rains....

Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

Neight

google waterproof ultrasonic sensors.
There are loads of them to choose from.
you could make a small waterproof enclosure for the electronics, which should leave them fairly well protected.

The biggest hurdle to cross in my mind is placement.
How do you keep them from getting stolen or run over by drivers cutting through a space?

I like GoForSmoke's idea of putting them on poles, but that seems like a recipe for false readings.  vehicles have a range of heights and angles, and reading a space from above would have a much wider range to activate the signal.  There is also the possibility that a car could park and if the sonar didn't get bounced back directly, it may not even see the car.

Going from underneath would be much easier to code, and sounds more reliable to me.  But that leads us right back to the stolen or crushed possibilities.

absence of proof is not proof of absence

GoForSmoke

They had them on poles at intersections back in the 70's cranked up LOUD. That got switched for in-ground detectors.

From above you get a nice return distance to the space below. If the distance changes, something is there. Reflected at an angle, distance = maximum. Don't make the poles too high.

Will ultrasonic work in the rain or reflect from the drops?

Try a metal detector instead.

You still haven't gone into force/pressure sensors or capacitive sensors.

Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

172pilot

I know this is an old topic, but it's one I was researching now too, and came upon this discussion..  My application is that I am having some work done on my house, and would like to detect and report via SMS text message, when the construction trucks go up my driveway.  My idea was to use a 3 axis magnetometer (compass) mounted in some PVC pipe with an arduino and a GSM shield, hidden in some bushes next to my driveway.

I figured SOMEONE must have done this, but I can't find any evidence.

I just ran across this document, which seems to indicate that it will work perfectly:
http://masters.donntu.edu.ua/2007/kita/gerus/library/amr.pdf

I'll report back my findings after I finish my build, just in case someone else stumbles on this thread.
-Steve

michinyon

For a driveway,  the easiest might be an IR beam-interruption scheme.

Go Up